Global Server Load Balancing (GSLB) based on Domain Name System (DNS) is an essential technology used in modern day data centers. GSLB allows a service provider to distribute workloads across multiple data centers. As a result, GSLB facilitates more evenly distributed traffic, business continuance, and disaster recovery. GSLB devices can be deployed with each data center and registered with an upper-level DNS server. These GSLB devices are typically synchronized with respect to the data centers' service state. The GSLB devices can resolve DNS queries (e.g., by returning the IP address of a selected data center) based on defined load-balancing policies, either static or dynamic. In addition, the GSLB devices typically monitor the health status of all the services independently. However, when a customer maintains a large number of data centers, registering a corresponding number of GSLB devices with a third-party DNS service can be difficult. It can also be costly, both in terms of bandwidth consumption and computation, to synchronize the data-center state information across different GSLB devices. As the number of data centers increases, the associated high capital expenditure (CapEx) and operational expenditure (OpEx), increased management and configuration overhead, scalability issues, and resilience issues can make the current GSLB solutions prohibitively expensive.
Furthermore, the emergence of software-defined data centers (SDDCs) which facilitates a significantly increased number of virtual data centers can exacerbate the aforementioned problems. SDDC expands beyond server virtualization, and facilitates virtualization of a wide variety of data center resources and services by operating data centers on community hardware rather than dedicated hardware devices SDDC is capable of providing customers with virtual data centers (VDC), which require network isolation, large layer 2 broadcast domains, dedicated network services, and greater scalability. A single hardware-based GSLB device dedicated to a physical data center might not be sufficient to meet such requirements.
In an SDDC environment, a physical data center (also known as a site) may support multiple tenants, each demanding dedicated GSLB service. As the number of sites increases and the number of customers being supported also increases, a large number of GSLB devices (which are likely to be virtualized) are needed. For example, for the virtual desktop application, the number of data center sites may exceed 50, and the number of GSLB devices needed per site may be even larger, such as hundreds or thousands. Current GSLB technologies are not suited for scaling up because registering such a large number (>1000) of GSLB devices to upper-level DNS servers is nearly impossible. In addition, heartbeat monitoring, collaboration, and synchronization among a large number of GSLB devices can be extremely troublesome, especially over the Internet.